Temporary bipolar epicardial atrial and ventricular pacing wires are routinely placed after major cardiac surgical procedures. Transitory changes in heart rate and rhythms following cardiac surgery are common and include sinus bradycardia, junctional rhythms, and atrioventricular heart blocks. Sinus bradycardia responds to simple atrial pacing in the range of 90-110 beats/minute. In contrast, atrioventricular blocks require both atrial and ventricular pacing to normalize atrioventricular synchrony. In fact, synchronization of atrial and ventricular contractions through the maintenance of normal sinus rhythm in the postoperative setting may account for up to 25% of the cardiac output. Tachyarrythnias are the most frequent arrythmia occurring postoperatively in some form in up to 64% of cardiac surgery patients. These fast rhythms are very detrimental and may result in atrioventricular dyssynchrony and thus, inefficient cardiac output. Overdrive atrial and atrioventricular pacing at a rate faster than the patient's spontaneous sinus rate usually suppresses paroxysmal atrial tachycardia. Atrial flutter can be interrupted through entrainment with atrial pacing at a rate slightly greater than the atrial flutter rate to recapture the atria. Following recapture, termination of the pacing is usually followed by a return to normal sinus rhythm. Rapid atrial stimulation (pacing) at rates up to 600 beats per minute for periods of less than one second may also be used in cases of atrial flutter to interrupt the flutter cycle. In some cases, atrial fibrillation, the most common postoperative supraventricular arrhythmia following cardiac surgery can also be converted using entrainment or rapid atrial pacing.
Postoperative ventricular tachyarrhythmias are potentially fatal. Differentiating ventricular tachycardia from sinus tachycardia with a bundle branch block or a supraventricular tachyarrythmia with aberrant conduction may be difficult. Direct recording from the epicardial atrial and ventricular bipolar pacing electrodes can lead to the definitive diagnosis which will direct the manner of treatment and prevent possible complications from inadvertent treatment.
Temporary atrial or atrioventricular pacing may decrease the need for inotropic support in the immediate postoperative period. Temporary pacing may be required for up to 48 hours for treatment of postoperative bradyarrhythmias. Routinely, most epicardial leads are left in place for up to 96 to 120 hours. Indwelling epicardial leads are potential sources for infection and may result in the development of mediastinitis. Mediastinitis can occur in up to 2% of postoperative cardiac surgery patients. Wound exploration, debridement, and surgical drainage are often required to treat this serious postoperative complication. At the time of removal, these epicardial leads, which are sewn into the myocardium, are pulled out with manual traction potentially resulting in further patient morbidity.
The current invention attempts to eliminate these problems of infection and lead removal by placing an implantable small pacing electrode within the myocardium that does not require removal and is operated via radio frequency.